Photodetector and display device

ABSTRACT

According to one embodiment, a photodetector includes a sensor unit including at least one photosensor, a liquid crystal element including a first substrate includes a plurality of first control electrodes, a second substrate including a second control electrode, and a liquid crystal layer held between the first substrate and the second substrate, a liquid crystal controller which controls a voltage to be applied to the liquid crystal layer for forming a first lens that is opposed to the photosensor in the liquid crystal layer, and a sensor controller which controls the sensor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 15/917,961,filed Mar. 12, 2018, which is based upon and claims the benefit ofpriority from Japanese Patent Application No. 2017-048581, filed Mar.14, 2017, the entire contents of which are incorporated herein byreference.

FIELD

Embodiments described herein relate generally to a photodetector and adisplay device.

BACKGROUND

For example, an image display device comprising a diffusion-controlliquid crystal panel and a liquid crystal display panel has beenproposed. The diffusion-control liquid crystal panel can switch a statebetween a lens formation state of diffusing linearly polarized light,oscillating in a predetermined direction, of light having directivity ina specific direction, and a non-lens formation state of transmitting thelight while maintaining the directivity of the light. In the lensformation state, a plurality of liquid crystal micro-lenses are formedby applying a voltage to a liquid crystal layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration example of aphotodetector PDT of the present embodiment.

FIG. 2 is a cross-sectional view showing a configuration example of aliquid crystal element LD.

FIG. 3 is a plan view showing a configuration example of the liquidcrystal element LD.

FIG. 4 is an illustration for explaining a first lens 5 formed in aliquid crystal layer 53.

FIG. 5 is an illustration for explaining the function of the first lens5 illustrated in FIG. 4.

FIG. 6 is an illustration for explaining another shape of the first lens5 formed in the liquid crystal layer 33.

FIG. 7 is an illustration showing a configuration example of thephotodetector PDT of the present embodiment.

FIG. 8 is a flowchart for explaining an example of control of thephotodetector PDT.

FIG. 9 is an illustration showing an example of a first lens formed inthe liquid crystal layer 53.

FIG. 10 is an illustration showing another configuration example of thephotodetector PDT of the present embodiment.

FIG. 11 is an illustration showing yet another configuration example ofthe photodetector PDT of the present embodiment.

FIG. 12 is an illustration showing yet another configuration example ofthe photodetector PDT of the present embodiment.

FIG. 13 is an illustration showing yet another configuration example ofthe photodetector PDT of the present embodiment.

FIG. 14 is an illustration showing a configuration example of a solarsystem SSYS, which is an example of application of the photodetectorPDT.

FIG. 15 is a flowchart for explaining an example of control of the solarsystem SSYS shown in FIG. 14.

FIG. 16 is an illustration showing yet another configuration example ofthe photodetector PDT of the present embodiment.

FIG. 17 is an illustration for explaining the function of the liquidcrystal element LD and a modulation element MD shown in FIG. 16.

FIG. 18 is a cross-sectional view showing a configuration example of themodulation element MD.

FIG. 19 is an illustration for explaining a modulation portion MA and anon-modulation portion NMA formed in the modulation element MD.

FIG. 20 is an illustration for explaining an example of control of thephotodetector PDT comprising the modulation element MD shown in FIGS. 16and 18.

FIG. 21 is an illustration for explaining another example of control ofthe photodetector PDT comprising the modulation element MD shown inFIGS. 16 and 18.

FIG. 22 is an illustration showing another configuration example of thephotodetector PDT of the present embodiment.

FIG. 23 is an illustration showing the basic structure and an equivalentcircuit of a display device DSP.

FIG. 24 is a plan view showing a configuration example of the displaydevice DSP shown in FIG. 23.

FIG. 25 is a cross-sectional view showing a configuration example of thedisplay device DSP shown in FIG. 23.

DETAILED DESCRIPTION

In general, according to one embodiment, a photodetector comprises: asensor unit comprising at least one photosensor; a liquid crystalelement comprising a first substrate comprising a plurality of firstcontrol electrodes, a second substrate comprising a second controlelectrode, and a liquid crystal layer held between the first substrateand the second substrate; a liquid crystal controller which controls avoltage to be applied to the liquid crystal layer for forming a firstlens that is opposed to the photosensor in the liquid crystal layer; anda sensor controller which controls the sensor unit.

According to another embodiment, a display device comprises: a firstsubstrate comprising a photosensor, a plurality of first controlelectrodes, and a pixel electrode; a second substrate comprising alight-shielding body including an opening opposed to the photosensor, asecond control electrode arranged at the opening, and a commonelectrode; and a liquid crystal layer held between the first substrateand the second substrate, the liquid crystal layer including a firstregion between the photosensor and the opening, and a second regionbetween the pixel electrode and the common electrode.

Embodiments will be described hereinafter with reference to theaccompanying drawings. The disclosure is merely an example, and properchanges within the spirit of the invention, which are easily conceivableby a skilled person, are included in the scope of the invention as amatter of course. In addition, in some cases, in order to make thedescription clearer, the widths, thicknesses, shapes, etc., of therespective parts are illustrated in the drawings schematically, ratherthan as an accurate representation of what is implemented. However, suchschematic illustration is merely exemplary, and in no way restricts theinterpretation of the invention. In addition, in the specification anddrawings, structural elements which function in the same or a similarmanner to those described in connection with preceding drawings aredenoted by like reference numbers, and redundant detailed descriptionthereof is omitted unless necessary.

FIG. 1 is a block diagram showing a configuration example of aphotodetector PDT of the present embodiment.

The photodetector PDT comprises a sensor unit SS, a liquid crystalelement LD, and a controller CT which controls the sensor unit SS andthe liquid crystal element ID. Details of the sensor unit SS and theliquid crystal element LD will be described later. The controller CTcomprises a timing controller TCT, a memory unit M, a liquid crystalcontroller LCT, and a sensor controller SCT. The timing controller TCTcontrols the liquid crystal controller LCT and the sensor controllerSCT, on the basis of various kinds of data, etc., stored in the memoryunit M. In one example, the memory unit M stores data regarding avoltage to be applied to a liquid crystal layer, which will be describedlater, for forming a lens of a predetermined shape in the liquid crystallayer. The liquid crystal controller LCT is configured to control theliquid crystal element LD, and applies a predetermined voltage to theliquid crystal layer, on the basis of the data stored in the memory unitM. The sensor controller SCT is configured to control the sensor unitSS, drives a photosensor provided in the sensor unit SS, and measures anoutput from the photosensor. Further, the sensor controller SCT outputsa measurement result of the output from the photosensor to an externaldevice OTD. Furthermore, the sensor controller SCT outputs themeasurement result to the liquid crystal controller LCT for feedbackcontrolling the liquid crystal element LD. An example of control of eachunit will be described later.

FIG. 2 is a cross-sectional view showing a configuration example of theliquid crystal element LD. While a first direction X, a second directionY, and a third direction Z in the drawing are orthogonal to each other,they may cross each other at an angle other than 90 degrees.

The liquid crystal element LD comprises a first substrate 51, a secondsubstrate 52, a liquid crystal layer 53, a first control electrode E1,and a second control electrode E2. In the example illustrated, the firstcontrol electrode E1 is provided on the first substrate 51, and thesecond control electrode E2 is provided on the second substrate 52.However, the first control electrode E1 and the second control electrodeE2 may both be provided on the same substrate, that is, on the firstsubstrate 51 or the second substrate 52.

The first substrate 51 comprises a transparent insulating substrate 511,the first control electrode E1, an alignment film 512, and a feeder 513.The first control electrode E1 is located between the insulatingsubstrate 511 and the liquid crystal layer 53. A plurality of firstcontrol electrodes E1 are arranged at intervals in the first direction Xin an effective area 50A. In one example, a width of each of the firstcontrol electrodes E1 along the first direction X is less than or equalto an interval between adjacent first control electrodes E1 along thefirst direction X. The alignment film 512 covers the first controlelectrodes E1, and is in contact with the liquid crystal layer 53. Thefeeder 513 is located in a non-effective area 50B outside the effectivearea 50A.

The second substrate 52 comprises a transparent insulating substrate521, the second control electrode E2, and an alignment film 522. Thesecond control electrode E2 is located between the insulating substrate521 and the liquid crystal layer 53. The second control electrode E2 is,for example, a single plate electrode which is located on substantiallythe entire surface of the effective area 50A, and also extends to thenon-effective area 50B. In the effective area 50A, the second controlelectrode E2 is opposed to the first control electrode E1 via the liquidcrystal layer 53. The second control electrode E2 is opposed to thefeeder 513 in the non-effective area 50B. The alignment film 522 coversthe second control electrodes E2, and is in contact with the liquidcrystal layer 53.

Each of the insulating substrates 511 and 521 is, for example, a glasssubstrate or a resin substrate. Each of the first control electrode E1and the second control electrode E2 is formed of a transparentconductive material such as indium tin oxide (ITO) or indium zinc oxide(IZO). Each of the alignment films 512 and 522 is, for example, ahorizontal alignment film, and is subjected to alignment treatment inthe first direction X.

The first substrate 51 and the second substrate 52 are bonded to eachother by a sealant 54 in the non-effective area 50B. The sealant 54includes a conductive material 55. The conductive material 55 isinterposed between the feeder 513 and the second control electrode E2,and electrically connects the feeder 513 and the second controlelectrode E2.

The liquid crystal layer 53 is held between the first substrate 51 andthe second substrate 52. The liquid crystal layer 53 is formed of, forexample, a liquid crystal material having the positive dielectricanisotropy. The first control electrode E1 and the second controlelectrode E2 apply a voltage, to the liquid crystal layer 53, forforming a first lens 5 in the liquid crystal layer 53.

The liquid crystal controller LCT controls the voltage to be applied tothe liquid crystal layer 53. By controlling the voltage to be applied toeach of the first control electrode E1 and the second control electrodeE2, the liquid crystal controller LCT can switch a mode between a modein which the first lens 5 is formed in the liquid crystal layer 53 and amode in which a lens is not formed in the liquid crystal layer 53.Further, by controlling the voltage to be applied to each of the firstcontrol electrodes E1, the liquid crystal controller LCT can switch amode between a mode in which the first lens 5 is formed at a firstposition of the liquid crystal layer 53 and a mode in which the firstlens 5 is formed at a second position, which is different from the firstposition, of the liquid crystal layer 53. Furthermore, by controllingthe voltage to be applied to each of the first control electrodes E1,the liquid crystal controller LCT can switch a mode between a mode inwhich the first lens 5 of a first shape is formed in the liquid crystallayer 53 and a mode in which the first lens 5 of a second shape, whichis different from the first shape, is formed in the liquid crystal layer53. The illustrated example corresponds to a case where a single firstlens 5 is formed in the liquid crystal layer 53. However, a plurality offirst lenses 5 may be formed in the liquid crystal layer 53.

FIG. 3 is a plan view showing a configuration example of the liquidcrystal element LD. FIG. 3(a) is a plan view of the first substrate 51,and FIG. 3(b) is a plan view of the second substrate 52.

In the first substrate 51 shown in FIG. 3(a), the sealant 54 is formedin a frame shape. The first control electrodes E1 are located at aninner side surrounded by the sealant 54, and are arranged at intervalsin the first direction X. Each of the first control electrodes E1 is,for example, a strip electrode extending in the second direction Y.Alternatively, the first control electrodes E1 may each be a stripelectrode extending in the first direction X, or may be island-shapedelectrodes arranged in the first direction X and the second direction Y.The shape of the island-shaped electrode is polygonal, such asrectangular or hexagonal, or circular. The feeder 513 extends in thesecond direction Y at a position overlapping the sealant 54. At least apart of the conductive material 55 included in the sealant 54 overlapsthe feeder 513. A wiring substrate 9 is connected to the first substrate51, and electrically connects each of the first control electrodes E1and the feeder 513 with the liquid crystal controller LCT.

In the second substrate 52 shown in FIG. 3(b), the second controlelectrode E2 is formed rectangular, and includes an end portion E2Eextending in the second direction Y. The end portion E2E overlaps thefeeder 513 and the conductive material 55. That is, the second controlelectrode 52 is electrically connected to the liquid crystal controllerLCT via the conductive material 55 and the feeder 513.

FIG. 4 is an illustration for explaining the first lens 5 formed in theliquid crystal layer 53. FIG. 4 illustrates only the structuresnecessary for explanation. Here, a case of applying a voltage, which isdifferent from that applied to first control electrodes E11 and E12, tothe second control electrode E2 will be described.

In one example, as described above, the liquid crystal layer 53 has thepositive dielectric anisotropy. Liquid crystal molecules 53M included inthe liquid crystal layer 53 are initially aligned such that their majoraxes are aligned in the first direction X in a state where an electricfield is not formed, and are aligned such that the major axes of theliquid crystal molecules 53M are aligned along an electric field in astate where the electric field is formed.

In one example, a voltage of 6V is applied to the first controlelectrode E11, a voltage of −6V is applied to the first controlelectrode E12, and a voltage of 0V is applied to the second controlelectrode E2. In regions in which the first control electrodes E11 and512 are opposed to the second control electrode E2, an electric fieldalong the third direction Z is formed. Therefore, the liquid crystalmolecules 53M are aligned such that their major axes are aligned alongthe third direction Z. In a region between the first control electrodeE11 and the first control electrode E12, an electric field which istilted with respect to the third direction Z is formed. Therefore, theliquid crystal molecules 53M are aligned such that their major axes aretilted with respect to the third direction Z. In an intermediate region,which is a region intermediate between the first control electrode E11and the first control electrode E12, an electric field is hardly formedor an electric field along the first direction X is formed. Therefore,the liquid crystal molecules 53M are aligned such that their major axesare aligned along the first direction X. The liquid crystal molecule 53Mhas refractive anisotropy Δn. Accordingly, the liquid crystal layer 53has a refractive-index distribution according to an alignment state ofthe liquid crystal molecules 53M. In other words, the liquid crystallayer 53 has a retardation distribution which is represented by Δn·d ora phase distribution, where d is a thickness of the liquid crystal layer53 along the third direction Z. Thickness d is, for example, 10 to 100μm. The first lens 5 shown by a dotted line in the drawing is one thatis formed by the refractive-index distribution, retardationdistribution, or phase distribution described above. The illustratedfirst lens 5 functions as a convex lens. Also, the illustrated firstlens 5 has a shape that is symmetrical with respect to a normal N of theliquid crystal element LD.

In the present embodiment, a system formed by combining the liquidcrystal layer 53 including liquid crystal molecules which are initiallyaligned substantially horizontally along a substrate main surface and anelectric field formed along a direction intersecting the substrate mainsurface has been explained, as an example of the liquid crystal elementLD comprising the first lens 5. However, the liquid crystal element LDcomprising the first lens 5 is not limited to the above. For example, aliquid crystal layer including liquid crystal molecules which areinitially aligned substantially perpendicularly to the substrate mainsurface may be combined, or the liquid crystal layer 53 may be combinedwith an electric field formed along the substrate main surface. In otherwords, as long as the system can vary the refractive-index distributionaccording to an electric field applied to the liquid crystal layer, aliquid crystal element comprising the first lens 5 can be realized. Thesubstrate main surface mentioned above refers to an X-Y plane defined bythe first direction X and the second direction Y.

FIG. 5 is an illustration for explaining the function of the first lens5 illustrated in FIG. 4.

Here, when a traveling direction of light is along the third directionZ, linearly polarized light having an oscillation plane along the firstdirection X is referred to as first polarized light POL1, and linearlypolarized light having an oscillation plane along the second direction Yis referred to as second polarized light POL2. Note that the travelingdirection of light is opposite to a direction indicated by an arrowrepresenting the third direction Z in the example illustrated. The firstpolarized light POL1 is shown by an arrow having a horizontal stripepattern in the drawing, and the second polarized light POL2 is shown byan arrow having a slanting stripe pattern in the drawing. Light L is,for example, natural light having random oscillation planes, and isassumed to enter from an outer surface 521A of the insulating substrate521, and travel from the second substrate 52 toward the first substrate51.

The first lens 5 has different functions on the first polarized lightPOL1 and the second polarized light POL2, respectively. That is, of thenatural light L, the first lens 5 transmits the second polarized lightPOL2 practically without refracting the second polarized light POL2, andrefracts the first polarized light POL1. In other words, the first lens5 exhibits a convergence function on mainly the first polarized lightPOL1.

FIG. 6 is an illustration for explaining another shape of the first lens5 formed in the liquid crystal layer 53.

The illustrated first lens 5 is a lens which is unsymmetrical withrespect to the normal N. In a first region 531 on the left side of thedrawing, that is, the region extending over the first control electrodesE11 to E13, and a second region 532 on the right side of the drawing,that is, the region extending over the first control electrodes E14 toE16, the first lens 5 has different refractive-index distributions. Sucha first lens 5 can be formed by setting the voltages of the firstcontrol electrodes E11 to E17 to, for example, 6V, 5V, 4V, 3V, 2V, 1V,and 6V, respectively, and setting the voltage of the second controlelectrode E2 to 0V.

FIG. 7 is an illustration showing a configuration example of thephotodetector PDT of the present embodiment.

The sensor unit SS comprises a substrate 21, and a photosensor 22mounted on the substrate 21. In the example illustrated, the sensor unitSS comprises a single photosensor 22, but may alternatively comprise aplurality of photosensors 22. As described above, the liquid crystalelement LD comprises the first substrate 51, the second substrate 52,and the liquid crystal layer 53, and details of these elements have beenexplained above. The first substrate 51 and the second substrate 52 bothhave optical transmissivity. A light receiving surface 22A of thephotosensor 22 is located directly under the first substrate 51. Thelight receiving surface 22A may be spaced apart from the first substrate51 or may be in contact with the first substrate 51. The first lens 5formed in the liquid crystal layer 53 is opposed to the photosensor 22.The photosensor 22 is arranged at a position where light incident on theliquid crystal element LD is converged by the first lens 5. Thephotosensor 22 outputs a signal according to the intensity of thereceived light. The sensor controller SCT measures the output from thephotosensor 22.

An example illustrated in FIG. 7(a) shows the state in which the light Lincident on the liquid crystal element LD in a direction substantiallyparallel to the normal N is converged by the first lens 5. The firstlens 5 illustrated is a lens having a shape that is symmetrical withrespect to the normal N of the liquid crystal element LD. An exampleillustrated in FIG. 7(b) shows the state in which the light L incidenton the liquid crystal element LD in a direction substantially inclinedwith respect to the normal N at an angle of θ1 is converged by the firstlens 5. The first lens 5 illustrated is a lens having a shape that isunsymmetrical with respect to the normal N of the liquid crystal elementLD. The first lens 5 having such shapes is formed by controlling of theliquid crystal element LD by the liquid crystal controller LCT. Notethat the light converged as illustrated in the drawing is mainly thefirst polarized light POL1, as has been explained with reference to FIG.5.

The controller CT can determine an incident direction of the light L, onthe basis of the shape of the first lens 5 formed by the control of theliquid crystal controller LCT, and the output from the photosensor 22measured by the sensor controller SCT. An example of such control by thecontroller CT will be described below.

FIG. 8 is a flowchart for explaining an example of control of thephotodetector PDT. Note that the memory unit M shown in FIG. 1 stores inadvance a first voltage V1 for forming a first lens 5L of a first shapein the liquid crystal layer 53, a second voltage V2 for forming a firstlens 5M of a second shape different from the first shape, and a thirdvoltage V3 for forming a first lens 5R of a third shape different fromthe first shape and the second shape.

In the controller CT, the liquid crystal controller LCT applies, to theliquid crystal layer 53, the first voltage V1 read from the memory unitM at a predetermined timing based on control by the timing controllerTCT (step ST11). The first lens 5L of the first shape is thereby formedin the liquid crystal layer 53. In one example, as shown in FIG. 9(a),in a state in which voltages of the first control electrodes E11 to E17arranged in the first direction X are set such that they are graduallyreduced relative to a voltage of the second control electrode E2, thefirst lens 5L that is unsymmetrical extending over the first controlelectrodes E11 to E17 is formed. The voltage applied to the firstcontrol electrodes E11 to E17 and the second control electrode E2 atthis time corresponds to the first voltage V1 for forming the first lens5L.

Further, the sensor controller SCT measures the output from thephotosensor 22 in a state where the first lens 5L is formed (step ST12).

Next, the liquid crystal controller LCT applies, to the liquid crystallayer 53, the second voltage V2 read from the memory unit M at apredetermined timing based on the control by the timing controller TCT(step ST13). The first lens 5M of the second shape is thereby formed inthe liquid crystal layer 53. In one example, as shown in FIG. 9(b), in astate in which the voltages of mainly the first control electrodes E11and E17 are set to be the same, and the voltages of the first controlelectrodes E12 to E16 are each set to 0V or smaller than the voltage ofthe first control electrode E11, the first ions 5M that is symmetricalextending over the first control electrodes E11 to E17 is formed. Thevoltage applied to the first control electrodes E11 to E17 and thesecond control electrode E2 at this time corresponds to the secondvoltage V2 for forming the first lens 5M.

Further, the sensor controller SCT measures the output from thephotosensor 22 in a state where the first lens 5M is formed (step ST14).

Next, the liquid crystal controller LCT applies, to the liquid crystallayer 53, the third voltage V3 read from the memory unit M at apredetermined timing based on the control by the timing controller TCT(step ST15). The first lens 5R of the third shape is thereby formed inthe liquid crystal layer 53. In one example, as shown in FIG. 9(c), in astate in which the voltages of the first control electrodes E11 to E17are set such that they are gradually increased relative to the voltageof the second control electrode E2, the first lens 5R that isunsymmetrical extending over the first control electrodes E11 to E17 isformed. The voltage applied to the first control electrodes E11 to E17and the second control electrode E2 at this time corresponds to thethird voltage V3 for forming the first lens 5R.

Further, the sensor controller SCT measures the output from thephotosensor 22 in a state where the first lens 5R is formed (step ST16).After that, the sensor controller SCT compares the outputs measured atthe respective timings, and determines a direction in which the maximumoutput can be obtained as being the incident direction of light (stepST17). For example, when the maximum output is obtained in a state wherethe first lens 5L of the first shape shown in FIG. 9(a) is formed, itcan be determined that the incident direction of light is a directioninclined toward the left side of the drawing with respect to the normalN at an angle of θ11. Further, when the maximum output is obtained in astate where the first lens 5M of the second shape shown in FIG. 9(b) isformed, it can be determined that the incident direction of light is adirection along the normal N. Furthermore, when the maximum output isobtained in a state where the first lens 5R of the third shape shown inFIG. 9(c) is formed, it can be determined that the incident direction oflight is a direction inclined toward the right side of the drawing withrespect to the normal N at an angle of θ12.

Note that the first lens 5 may be shaped in a variety of forms otherthan the three shapes illustrated in FIG. 9, and the output from thephotosensor 22 can be measured every time a new shape is formed.Further, the shape of the first lens 5 can be made to changecontinuously from the first lens 5L of the first shape shown in FIG. 9to the first lens 5R of the third shape through the first lens 5M of thesecond shape, and an angle of incidence of the light can be measured bymeasuring the output from the photosensor 22 every time the shape of thefirst lens 5L is changed.

According to the present embodiment, the liquid crystal element LDcapable of forming the first lens 5 having the function of convergingthe incident light at a position opposed to she photosensor 22 isprovided. Since the first lens 5 is formed by the liquid crystal layer53, by controlling the alignment state of the liquid crystal molecules,the shape of the first lens 5 can be changed. In a photodetectorstructured by combining an optical lens formed by glass, resin, or thelike, and the photosensor, a movement mechanism for changing the angleor orientation of the photosensor, etc., is required. However, since thephotodetector PDT of the present embodiment can change the shape of thefirst lens 5, the incident direction of light can be determined withoutchanging the angle or orientation of the first lens 5 and thephotosensor 22. Accordingly, according to the present embodiment, ascompared to a movable photodetector, a photodetector PDT which is smallin size and low in cost can be provided.

Next, another configuration example of the photodetector PDT will beexplained.

FIG. 10 is an illustration showing another configuration example of thephotodetector PDT of the present embodiment. The configuration exampleillustrated in FIG. 10 is different from the configuration exampleillustrated in FIG. 7 in that the sensor unit SS comprises a pluralityof photosensors 221 to 225 on the substrate 21. In the exampleillustrated, the photosensors 221 to 225 are arranged in the firstdirection X. Each of the photosensors 221 to 225 outputs a signalaccording to the intensity of the received light. Note that the numberof photosensors 22 provided in the sensor unit SS is not limited to thatof the illustrated example.

The first lens 5 formed in the liquid crystal layer 53 is opposed to thephotosensors 221 to 225. In the present configuration example, the shapeof the first lens 5 does not change. That is, a voltage applied to theliquid crystal layer 53 is constant, and for example, the second voltage72 for forming the first lens 5M described above is applied to the firstcontrol electrode E1 and the second control electrode E2.

An example illustrated in FIG. 10(a) shows the state in which the lightL incident on the liquid crystal element LD in a direction substantiallyparallel to the normal N is converged by the first lens 5. The light Lincident from outside in a normal direction is converged on thephotosensor 223 by the first lens 5. In this case, of the plurality ofphotosensors, the photosensor 223 gives the maximum output. An exampleillustrated in FIG. 10(b) shows the state in which the light L incidenton the liquid crystal element LD in a direction substantially inclinedwith respect to the normal N at the angle of θ1 is converged by thefirst lens 5. The light L being incident obliquely is converged to thephotosensor 224 by the first lens 5. In this case, of the plurality ofphotosensors, the photosensor 224 gives the maximum output.

As can be seen, even in a structure in which the shape of the first lens5 does not change, by comparing the outputs from the plurality ofphotosensors 22 arranged directly under the first lens 5, the incidentdirection of the light L can be determined. Further, since the shape ofthe first lens 5 does not need to be changed, control for forming thefirst lens 5 can be simplified. Note that the first lens 5 capable ofchanging its shape likewise the configuration example of FIG. 7 and theconfiguration example of FIG. 10 comprising the plurality ofphotosensors 22 may be combined.

A combination of a single first lens 5 and multiple photosensors 22 canbe changed variously.

In an example illustrated in FIG. 11, the first lens 5 is a convex lenswhich includes a curved surface having a generatrix along the seconddirection Y, and projects in the third direction Z. The photosensors 22are arranged in the first direction X. With the first lens 5illustrated, a convergence position is shifted in the first direction Xin accordance with the incident direction of the light. Accordingly, bycomparing the outputs from the photosensors 22 arranged in the firstdirection X, the incident direction of the light L in an X-Z planedefined by the first direction X and the third direction Z can bedetermined.

In an example illustrated in FIG. 12, the first lens 5 is a convex lenswhich is substantially circular in the X-Y plane defined by the firstdirection X and the second direction Y, and projects in the thirddirection Z. The photosensors 22 are arranged in a matrix in the firstdirection X and the second direction Y. With the first lens 5illustrated, a convergence position is shifted in the first direction Xand the second direction Y in accordance with the incident direction ofthe light. Accordingly, by comparing the outputs from the photosensors22 arranged in a matrix, an incident azimuth of the light L with thethird direction Z assumed as the center can be determined.

In an example illustrated in FIG. 13, a first lens 5X is a convex lenswhich includes a curved surface having a generatrix along the firstdirection X, and projects in the third direction Z. A first lens 5Y is aconvex lens which includes a curved surface having a generatrix alongthe second direction Y, and projects in the third direction Z. The firstlenses 5X and 5Y are arranged in the third direction Z. The photosensors22 are arranged in a matrix in the first direction X and the seconddirection Y. Also in this example, likewise the example illustrated inFIG. 12, the incident azimuth of the light L with the third direction Zassumed as the center can be determined.

Next, an example of application of the photodetector PDT of the presentembodiment will be described.

FIG. 14 is an illustration showing a configuration example of a solarsystem SSYS, which is an example of application of the photodetectorPDT. The solar system SSYS comprises a solar panel SPNL, thephotodetector PDT, a support body SPB, and a rotation mechanism RTM. Thesolar panel SPNL performs heating, cooling, electric power generation,etc., by using solar energy. The structure of the photodetector PDT isas described above. The support body SPB supports the solar panel SPNLand the photodetector PDT. The rotation mechanism RTM rotates thesupport body SPB. Not only is the rotation mechanism RTM rotated in ahorizontal plane as shown by arrow A in the drawing, but is also drivenin a direction of an elevation angle with respect to the horizontalplane as shown by arrow B in the drawing. The photodetector PDT may beincorporated in the solar panel SPNL. Note that normal N1 of thephotodetector PDT should preferably be parallel to normal N2 of thesolar panel SPNL.

FIG. 15 is a flowchart for explaining an example of control of the solarsystem SSYS shown in FIG. 14.

First, the photodetector PDT determines the incident direction of lightby the configuration example explained with reference to FIGS. 7 to 9,or the configuration example explained with reference to FIGS. 10 to 13(step ST21). Further, the photodetector PDT determines whether a lightsource, that is, the sun is positioned in front of the solar panel SPNL,on the basis of the light incident direction which has been determined(step ST22). More specifically, the photodetector PDT determines whetherthe light source is positioned at the front by determining whether thelight incident direction which has been determined is parallel to normalN1 of the photodetector PDT. When it is determined that the light sourceis positioned at the front (in other words, the determined incidentdirection is parallel to normal N1) (Yes in step ST22), the flow returnsto step ST21 again. Meanwhile, when it is determined that the lightsource is not positioned at the front (in other words, the determinedincident direction is not parallel to normal N1) (No in step ST22), therotation mechanism RTM is driven (step ST23). The rotation mechanism RTMrotates the support body SPB such that normal N2 of the solar panel SPNLfaces the light source.

By this control, it is possible to direct the solar panel SPNL towardthe light source so as to follow the light source whose positionchanges, and the efficiency of use of the solar energy can be improved.

Next, yet another configuration example of the photodetector PDT will beexplained.

FIG. 16 is an illustration showing yet another configuration example ofthe photodetector PDT of the present embodiment. A configuration exampleshown in FIG. 16 is different from the configuration example illustratedin FIG. 7 in that a modulation element MD which modulates the incidentlight is provided. The modulation element MD comprises a modulationportion MA which imparts a retardation to the incident light, and anon-modulation portion NMA which transmits the incident lightpractically without modulating the same. The modulation portion MAimparts, for example, a retardation of approximately λ/2 to the incidentlight. λ indicates a wavelength of the incident light. When the incidentlight is linearly polarized light, the modulation portion MA asdescribed above has the function of rotating a polarization plane of thelinearly polarized light by approximately 90 degrees. The modulationelement MD may be constituted by a liquid crystal element which canpartially control the retardation, or may be constituted by aretardation film partially having retardation. The modulation portion MAis smaller than the non-modulation portion NMA. In one example, a widthW1 of the modulation portion MA along the first direction X is smallerthan a width W2 of the non-modulation portion NMA along the firstdirection X. Although a detailed configuration example of the modulationelement MD will be described later, in the example illustrated, themodulation element MD comprises a third substrate 61 and a fourthsubstrate 62. The modulation portion MA and the non-modulation portionNMA are both located between the third substrate 61 and the fourthsubstrate 62. When the modulation element MD is constituted by a liquidcrystal element which will be described later, the modulation element MDis controlled by a modulation controller MCT.

In the example illustrated, the sensor unit SS is incorporated in themodulation element MD. That is, the photosensor 22 is located betweenthe third substrate 61 and the fourth substrate 62. The third substrate61 corresponds to a substrate on which the photosensor 22 is mounted.The sensor unit SS is controlled by the sensor controller SCT.

The liquid crystal element LD comprises a third control electrode E3 anda fourth control electrode E4 for forming a second lens 6 in the liquidcrystal layer 53, in addition to the first control electrode E1 and thesecond control electrode E2 for forming the first lens 5 in the liquidcrystal layer 53. Such a liquid crystal element LD is controlled by theliquid crystal controller LCT.

In one example, the third control electrode E3 is provided on the firstsubstrate 51 likewise the first control electrode E1, and can be formedof the same material as that of the first control electrode E1. Thefourth control electrode E4 is provided on the second substrate 52likewise the second control electrode E2, and can be formed of the samematerial as that of the second control electrode E2. Also, the secondcontrol electrode E2 and the fourth control electrode E4 may be formedintegrally. Each of the third control electrode E3 and the fourthcontrol electrode E4 is formed of a transparent conductive material suchas ITO or IZO. The third control electrode 53 is a strip electrodeextending in the second direction Y likewise the first control electrodeE1 shown in FIG. 3. The fourth control electrode E4 is a rectangularplate electrode likewise the second control electrode E2 shown in FIG.3. The third control electrode E3 and the fourth control electrode E4apply a voltage for forming the second lens 6 in the liquid crystallayer 53. The second lens 6 formed in the liquid crystal layer 53 isopposed to the modulation element MD. In the modulation element MD, themodulation portion MA is arranged at a position where the light isconverged by the second lens 6. The width W1 of the modulation portionMA is less than a width W3 of the second lens 6 along the firstdirection X (in other words, an interval between the third controlelectrodes 53 for forming the second lens 6). Note that an arrowrepresented by a solid line in the drawing denotes the first polarizedlight POL1 having an oscillation plane along the first direction X, andan arrow represented by a dotted line in the drawing denotes the secondpolarized light POL2 having an oscillation plane along the seconddirection Y. Also, similarly to the first lens 5 explained withreference to FIG. 9, the shape of the second lens 6 can be changedfreely by controlling a voltage to be applied to the third controlelectrode E3 and the fourth control electrode 54.

FIG. 17 is an illustration for explaining the function of the liquidcrystal element LD and the modulation element MD shown in FIG. 16. Ofthe light incident on the liquid crystal element LD, the first polarizedlight POL1 is converged by the second lens 6 and enters the modulationelement MD, as shown on the left side of the drawing. Almost all of thefirst polarized light POL1 enters the modulation portion MA, and isconverted into the second polarized light POL2. That is, the firstpolarized light POL1 which has entered the liquid crystal element LD isconverted into the second polarized light POL2, and passes through themodulation element MD.

Meanwhile, of the light incident on the liquid crystal element LD, thesecond polarized light POL2 enters the modulation element MD practicallywithout being converged by the second lens 6, as shown on the right sideof the drawing. The second polarized light POL2 enters the modulationportion MA and the non-modulation portion NMA. As stated above, sincethe non-modulation portion NMA is greater than the modulation portionMA, light incident on the non-modulation portion NMA of the lightincident on the modulation element MD is more than light incident on themodulation portion MA. In other words, most of the second polarizedlight POL2 incident on the modulation element MD is transmitted with itspolarization plane unchanged because it passes through thenon-modulation portion NMA which does not modulate the light. Part ofthe second polarized light POL2, which is incident on the modulationelement MD, enters the modulation portion MA, and is converted into thefirst polarized light POL1. As described above, the second polarizedlight POL2 made incident on the liquid crystal element LD passes throughthe modulation element MD by mostly being maintained as the secondpolarized light POL2.

According to such a configuration example, regardless of a direction ofpolarization of light incident on the liquid crystal element LD, thepolarization directions of light beams which have passed through themodulation element MD can be made substantially uniform. Light beamswhose polarization directions are uniform are suitable as theillumination light of a liquid crystal display device, for example.

FIG. 18 is a cross-sectional view showing a configuration example of themodulation element MD. Here, a case where the modulation element MD isconstituted by a liquid crystal element will be described. Such amodulation element MD is controlled by the modulation controller MCT.

The modulation element MD comprises the third substrate 61, the fourthsubstrate 62, a liquid crystal layer 63, a fifth control electrode E6,and a sixth control electrode E6. In the example illustrated, the fifthcontrol electrode E5 is provided on the third substrate 61, and thesixth control electrode E6 is provided on the fourth substrate 62.However, the fifth control electrode E5 and the sixth control electrodeE6 may both be provided on the same substrate, that is, on the thirdsubstrate 61 or the fourth substrate 62.

The third substrate 61 comprises a transparent insulating substrate 611,the fifth control electrode E5, an alignment film 612, and a feeder 613.The fifth control electrode E5 is located between the insulatingsubstrate 611 and the liquid crystal layer 63. A plurality of fifthcontrol electrodes 55 are arranged at intervals in the first direction Xin an effective area 60A. In one example, a width of each of the fifthcontrol electrodes E5 along the first direction X is greater than aninterval between adjacent fifth control electrodes E5 along the firstdirection X. The alignment film 612 covers the fifth control electrodesE5, and is in contact with the liquid crystal layer 63. The feeder 613is located in a non-effective area 60B outside the effective area 60A.

The fourth substrate 62 comprises a transparent insulating substrate621, the sixth control electrode E6, and an alignment film 622. Thesixth control electrode E6 is located between the insulating substrate621 and the liquid crystal layer 63. The sixth control electrode E6 is,for example, a single plate electrode which is located on substantiallythe entire surface of the effective area 60A, and also extends to thenon-effective area 60B. In the effective area 60A, the sixth controlelectrode E6 is opposed to the fifth control electrode E5 via the liquidcrystal layer 63. The sixth control electrode E6 is opposed to thefeeder 613 in the non-effective area 60B. The alignment film 622 coversthe sixth control electrode E6, and is in contact with the liquidcrystal layer 63.

Each of the insulating substrates 611 and 621 is, for example, a glasssubstrate or a resin substrate. Each of the fifth control electrode E5and the sixth control electrode E6 is formed of a transparent conductivematerial such as ITO or IZO. The fifth control electrode 65 is a stripelectrode extending in the second direction Y likewise the first controlelectrode E1 shown in FIG. 3. The sixth control electrode E6 is arectangular plate electrode likewise the second control electrode E2shown in FIG. 3. Each of the alignment films 612 and 622 is, forexample, a horizontal alignment film. In one example, the alignment film612 is subjected to alignment treatment along the second direction Y,and the alignment film 622 is subjected to alignment treatment along thefirst direction X.

The third substrate 61 and the fourth substrate 62 are bonded to eachother by a sealant 64 in the non-effective area 60B. The sealant 64includes a conductive material 65. The conductive material 65 isinterposed between the feeder 613 and the sixth control electrode E6,and electrically connects the feeder 613 and the sixth control electrodeE6.

The liquid crystal layer 63 is held between the third substrate 61 andthe fourth substrate 62. The liquid crystal layer 63 is formed of, forexample, a liquid crystal material having positive dielectricanisotropy. The fifth control electrode E5 and the sixth controlelectrode E6 apply a voltage for forming the modulation portion MA andthe non-modulation portion NMA shown in FIG. 17 to the liquid crystallayer 63.

The modulation controller MCT controls the voltage to be applied to theliquid crystal layer 63. By controlling the voltage applied to each ofthe fifth control electrode E5 and the sixth control electrode E6, themodulation controller MCT can form the modulation portion MA and thenon-modulation portion NMA in the liquid crystal layer 63. Further, bycontrolling the voltage applied to each of the fifth control electrodesE5, the modulation controller MCT can control the positions where themodulation portion MA and the non-modulation portion NMA are formed.Furthermore, by controlling the voltage applied to each of the fifthcontrol electrodes E5, the modulation controller MCT can control thesize of the modulation portion MA and the non-modulation portion NMAfreely.

FIG. 19 is an illustration for explaining the modulation portion MA andthe non-modulation portion NMA formed in the modulation element MD. FIG.19 illustrates only the structures necessary for explanation. Here, acase of applying a voltage, which is different from that applied to thesixth control electrode E6, to fifth control electrodes E51, E53, andE55, of a plurality of fifth control electrodes E51 to E55 arranged inthe first direction X, will be described.

In one example, the voltage of the fifth control electrodes E51, E53,and E55 is 6V, and the voltage of the fifth control electrodes E52 andE54, and the sixth control electrode E6 is 0V. Further, the liquidcrystal layer 63 has the positive dielectric anisotropy as stated above.Liquid crystal molecules 63M included in the liquid crystal layer 63 aretwisted-aligned by 90 degrees in a state where no electric field isformed. In other words, the liquid crystal molecules 63M near the fifthcontrol electrodes E51 to E53 are initially aligned such that theirmajor axes are aligned in the second direction Y, and the liquid crystalmolecules 63M near the sixth control electrode E6 are initially alignedsuch that their major axes are aligned in the first direction X.Further, the liquid crystal molecules 63M are aligned such that theirmajor axes are aligned along an electric field in a state where theelectric field is formed.

In each of regions in which the fifth control electrodes E51, E53, andE55 are opposed to the sixth control electrode E6, an electric fieldalong the third direction Z is formed. Therefore, the liquid crystalmolecules 63M are vertically aligned such that their major axes arealigned along the third direction Z. In each of regions in which thefifth control electrodes E52 and E54 are opposed to the sixth controlelectrode E6, an electric field is not formed. Therefore, the liquidcrystal molecules 63M are maintained in the initial alignment state, andtwisted-aligned.

Here, a case where the first polarized light POL1 enters the modulationelement MD is assumed. Of beams of the first polarized light POL1 whichenter from the fourth substrate 62, a beam of the first polarized lightPOL1, which enters a region in which the fifth control electrode E52 andthe sixth control electrode E6 are opposed to each other, is affected bythe twisted-aligned liquid crystal molecules 63M, and the polarizationplane is rotated. Thus, after the above first polarized light POL1passes through the liquid crystal layer 63, it is converted into thesecond polarized light POL2 having an oscillation plane along the seconddirection Y. Similarly in the region in which the fifth controlelectrode E54 is opposed to the sixth control electrode E6, thetransmitted light is converted into the second polarized light POL2.Meanwhile, the first polarized light POL1 incident on a region in whichthe fifth control electrode E53 and the sixth control electrode E6 areopposed to each other is hardly affected by the liquid crystal molecules63M that are vertically aligned. Thus, the above first polarized lightPOL1 passes through the liquid crystal layer 63 while maintaining itspolarization plane. Similarly in the regions in which the fifth controlelectrodes E51 and E55 are opposed to the sixth control electrode E6,the transmitted light is the first polarized light POL1.

In other words, regions in which the fifth control electrodes E51, E53,and 555 are opposed to the sixth control electrode E6 correspond to thenon-modulation portions NMA shown in FIG. 17, and regions in which thefifth control electrodes E52 and E54 are opposed to the sixth controlelectrode E6 correspond to the modulation portions MA shown in FIG. 17.

In the present embodiment, as an example of the modulation element MD, asystem obtained by combining the liquid crystal layer 63 includingliquid crystal molecules twisted-aligned in the initial alignment stateand an electric field produced along a direction intersecting thesubstrate main surface has been explained. However, the modulationelement MD is not limited to the above. That is, as long as the systemcan form a region which modulates the incident light in accordance witha voltage applied to the liquid crystal layer 63, and a region whichtransmits the incident light without modulating the same, such a systemis applicable to the modulation element MD described above.

FIG. 20 is an illustration for explaining an example of control of thephotodetector PDT comprising the modulation element MD shown in FIGS. 16and 18.

First, the controller CT determines the incident direction of light, onthe basis of the output from the photosensor 22, as in the configurationexample explained with reference to FIGS. 7 to 9, or the configurationexample explained with reference to FIGS. 10 to 13 (step ST31). Further,the controller CT controls the liquid crystal element LD, and forms thesecond lens 6 such that the light entering in the incident directionwhich has been determined converges to the modulation portion MA (stepST32). In the second lens 6 formed in a specific shape, the convergenceposition is shifted in accordance with the incident direction of thelight. In the control example explained in this specification, the shapeof the second lens 6 is changed so as to fix the convergence positionregardless of the incident direction of the light. In other words, thecontroller CT controls the voltage applied to the third controlelectrode E3 and the fourth control electrode E4 in order to form thesecond lens 6 of a desired shape whereby the modulation portion MAmatches with the convergence position.

By this control, even if the position of the modulation portion MA isfixed, the polarization directions of light beams which have passedthrough the modulation element MD can be made substantially uniformregardless of the incident direction of the light.

FIG. 21 is an illustration for explaining another example of control ofthe photodetector PDT comprising the modulation element MD shown inFIGS. 16 and 18.

First, the controller CT determines the incident direction of light, onthe basis of the output from the photosensor 22, as in the configurationexample explained with reference to FIGS. 7 to 9, or the configurationexample explained with reference to FIGS. 10 to 13 (step ST41). Further,the controller CT controls the modulation element MD, and forms themodulation portion MA at a place where the light entering in thedetermined incident direction is converged by the second lens 6 (stepST42). In the control example explained in this specification, theposition of the modulation portion MA is changed so that the modulationportion MA follows the convergence position which is shifted inaccordance with the incident direction of light, in a case where theshape of the second lens 6 is not varied. In other words, the controllerCT controls the voltage applied to the fifth control electrode E5 andthe sixth control electrode E6 so as to form the modulation portion MAat the convergence position of the incident light.

By such control, even if the shape of the second lens 6 is fixed, thepolarization directions of light beams which have passed through themodulation element MD can be made substantially uniform regardless ofthe incident direction of the light.

FIG. 22 is an illustration showing another configuration example of thephotodetector PDT of the present embodiment. The configuration exampleillustrated in FIG. 22 is different from the configuration exampleillustrated in FIG. 16 in that this configuration example includes anopening OP, in stead of the first lens 5, at a position opposed to thephotosensor 22. The liquid crystal element LD comprises alight-shielding body BM at a position different from where the secondlens 6 is formed. In the light-shielding body BM, the opening OP isformed. In one example, the opening OP is a pinhole, and has a diameterof approximately 50 to 100 μm. Alternatively, the opening OP may be aslit extending in the second direction Y. The photosensor 22 is locatedbetween the opening OP and the third substrate 61.

Also in this configuration example, the same advantage as that of theabove-described configuration example can be obtained.

Next, an example of a display device DSP will be explained.

FIG. 23 is an illustration showing the basic structure and an equivalentcircuit of the display device DSP.

The display device DSP includes a display area DA in which an image isdisplayed, and a non-display area NDA which surrounds the display areaDA. The display area DA comprises a plurality of pixels PX. Here, thepixel indicates a minimum unit which can be individually controlled inaccordance with a pixel signal, and exists in, for example, an areaincluding a switching element arranged at a position where a scanningline and a signal line, which will be described later, cross each other.The pixels PX are arrayed in a matrix in the first direction X and thesecond direction Y. Also, the display device DSP includes scanning lines(also referred to as gate lines) G (G1 to Gn), signal lines (alsoreferred to as data lines or source lines) S (S1 to Sm), a commonelectrode CE, etc., in the display area DA. The scanning lines G extendin the first direction X, and are arranged in the second direction Y.The signal lines S extend in the second direction Y, and are arranged inthe first direction X. Note that the scanning lines G and the signallines S do not necessarily extend linearly, but may be partially bent.The common electrode CE is disposed over the pixels PX. The scanninglines G are connected to a scanning line drive circuit GD, the signallines S are connected to a signal line drive circuit SD, and the commonelectrode CE is connected to a common electrode drive circuit CD. Thescanning line drive circuit GD, the signal line drive circuit SD, andthe common electrode drive circuit CD are controlled by the controllerCT.

Each of the pixels PX comprises a switching element SW, a pixelelectrode PE, the common electrode CE, a liquid crystal layer LC, andthe like. The switching element SW is constituted by a thin-filmtransistor (TFT), for example, and is electrically connected to thescanning line G and the signal line S. More specifically, the switchingelement SW includes a gate electrode WG, a source electrode WS, and adrain electrode WD. The gate electrode WG is electrically connected tothe scanning ling C. In the example illustrated, the electrodeelectrically connected to the signal line S is referred to as the sourceelectrode WS, and the electrode electrically connected to the pixelelectrode PE is referred to as the drain electrode WD. The scanning lineG is connected to the switching elements SW of the respective pixels PXarranged in the first direction X. The signal line S is connected to theswitching elements SW of the respective pixels PX arranged in the seconddirection Y.

The pixel electrode PE is electrically connected to the switchingelement SW. The common electrode CE is opposed to a plurality of pixelelectrodes PE. The pixel electrode PE and the common electrode CEfunction as a first display electrode and a second display electrodewhich apply a voltage to a liquid crystal layer 13. The pixel electrodePE and the common electrode CE are formed of a transparent conductivematerial such as ITO or IZO. A storage capacitance CS is formed between,for example, the common electrode CE and the pixel electrode PE.

Although the details of the structure of the display device DSP will notbe described here, the display device DSP has a structure correspondingto one of various modes including a twisted nematic (TN) mode, a polymerdispersed liquid crystal (PDLC) mode, an optically compensated bend(OCB) mode, an electrically controlled birefringence (ECB) mode, avertically aligned (VA) mode, a fringe field switching (FFS) mode, andin-plane switching (IPS) mode. Also, while explanation has been providedfor a case where each of the pixels PX is driven by an active method,the pixels PX may be driven by a passive method.

The photosensor 22 is incorporated in the display device DSP. In theexample illustrated, the photosensor 22 is arranged in the non-displayarea NDA. The photosensor 22 is controlled by the controller CT.

FIG. 24 is a plan view showing a configuration example of the displaydevice DSP shown in FIG. 23. The display device DSP includes a firstsubstrate SUB1 and a second substrate SUB2. The first substrate SUB1 andthe second substrate SUB2 are bonded to each other by a sealant SE. Thesealant SE is located in the non-display area NDA. In the non-displayarea NDA, a portion including downward-sloping hatch lines correspondsto a region where the light-shielding body BM is located, and a portionincluding crossed lines corresponds to a region where thelight-shielding body BM and the sealant SE overlap one another.

When a part of the non-display area NDA is increased, the photosensor 22overlaps the opening OP formed in the light-shielding body BM. In theexample illustrated in FIG. 24(a), the opening OP is a circular pinhole.In the example illustrated in FIG. 24(b), the opening OP is formed in aslit shape extending in the second direction Y. In either of theexamples, the photosensor 22 and the opening OP are located closer tothe display area DA than the sealant SE.

FIG. 25 is a cross-sectional view showing a configuration example of thedisplay device DSP shown in FIG. 23.

The first substrate 1 comprises an insulating substrate 100, aninsulating film 110, an alignment film 120, the switching element SW,the pixel electrode PE, the photosensor 22, the first control electrodeE1, etc. The insulating substrate 100 and the insulating film 110 areboth transparent. In the display area DA, the switching element SW isarranged between the insulating substrate 100 and the insulating film110. The pixel electrode PE is arranged between the insulating film 110and the alignment film 120, and is electrically connected to switchingelement SW.

In the non-display area NDA, the photosensor 22 is arranged between theinsulating substrate 100 and the insulating film 110. The photosensor 22is, for example, a PIN photodiode, and can be formed in the process offorming the switching element SW. The first control electrode E1 isarranged between the insulating film 110 and the alignment film 120. Thefirst control electrode E1 is located closer to the liquid crystal layerLC than the photosensor 22. A space between the illustrated two firstcontrol electrodes E1 overlaps the photosensor 22. In the exampleillustrated, the pixel electrode PE and the first control electrode E1are located in the same layer, and can be formed of the same material.In one example, the pixel electrode PE is a reflective electrode, and isformed of a reflective metal material such as aluminum or silver. Notethat the pixel electrode PE may be a transparent electrode formed ofITO, etc. The pixel electrode PE and the first control electrode E1 arelocated on the insulating film 110, and are covered with the alignmentfilm 120.

The second substrate SUB2 comprises an insulating substrate 200, aninsulating layer 210, a color filter 220, an overcoat layer 230, analignment film 240, the common electrode CE, the second controlelectrode E2, the light-shielding body BM, etc. The insulating substrate200 and the insulating layer 210 are both transparent. The insulatinglayer 210 is disposed over substantially the entire area of the displayarea DA, but is not arranged in an area where the first lens 5 is formedin the non-display area NDA. The insulating layer 210 is a transparentinsulating layer, and is formed of a transparent organic material. Thecolor filter 220 is arranged between the insulating layer 210 and theovercoat layer 230. The overcoat layer 230 covers the color filter 220.The common electrode CE is disposed between the overcoat layer 230 andthe alignment film 240. The common electrode CE is a transparentelectrode formed of ITO, etc.

In the non-display area NDA, the light-shielding body BM is disposedbetween the insulating substrate 200 and the alignment film 240, andincludes the opening OP. The opening OP is formed at a position opposedto the photosensor 22. The second control electrode E2 is arrangedbetween the insulating substrate 200 and the alignment film 240 in theopening OP. The second control electrode E2 can be formed of the samematerial as that of the common electrode CE. The common electrode CE andthe second control electrode E2 are covered with the alignment film 240.

The liquid crystal layer LC is held between the first substrate SUB1 andthe second substrate SUB2. The liquid crystal layer LC includes a firstregion LC1 between the photosensor 22 and the opening OP in thenon-display area NDA, and a second region LC2 in the display area DA.The first region LC1 has a first thickness D1 between the alignment film120 and the alignment film 240. The second region LC2 has a secondthickness D2 between the alignment film 120 and the alignment film 240.The first thickness D1 is greater than the second thickness D2. In oneexample, the second thickness D2 is approximately 2 to 4 μm, and thefirst thickness D1 is approximately 10 to 20 μm. A difference betweenthe first thickness D1 and the second thickness D2 is formed mainly bythe insulating layer 210. A thickness D3 of the insulating layer 210 isless than the first thickness D1, and is greater than the secondthickness D2. In one example, the thickness D3 is approximately 10 μm.In one example, the thickness D3 is three to four times greater than thesecond thickness D2.

As stated above, the first control electrode E1 and the second controlelectrode E2 apply a voltage for forming the first lens 5 to the firstregion LC1 of the liquid crystal layer LC. The first lens 5 is therebyformed directly above the photosensor 22. The first lens 5 converges thelight incident through the second substrate SUB2 on the photosensor 22.The photosensor 22 outputs a signal according to the intensity of thereceived light.

Further, the pixel electrode PE and the common electrode CE apply avoltage to the second region LC2 of the liquid crystal layer LC.Consequently, a retardation of the second region LC2 is changed. Morespecifically, in an off-state in which a voltage is not applied to thesecond region LC2 and an on-state in which a voltage is applied to thesecond region LC2, the alignment state of the liquid crystal moleculesincluded in the liquid crystal layer LC differs, and the retardation ischanged. In a reflective display device DSP in which the pixel electrodePE is a reflective electrode and the common electrode CE is atransparent electrode, by a difference in the retardation between theon-state and the off-state, the external light incident through thesecond substrate SUB2 is selectively reflected, and an image isdisplayed.

According to the display device DSP described above, on the basis of theoutput from the photosensor 22, the intensity of the external lightincident on the display device DSP can be measured, and the displayluminance of the display device DSP can be controlled in accordance withthe intensity of the external light. For example, when the intensity ofthe external light is low, by increasing the luminance of theillumination light which illuminates the display device DSP from theside at the second substrate SUB2, visibility of the displayed image canbe improved.

Further, on the basis of an output from the photosensor 22, the incidentdirection of light can be determined likewise the photodetector PDTdescribed above. Accordingly, the display device can be oriented in adirection which allows an observer to easily visually recognize thedisplay device DSP. For example, when the external light is regularlyreflected by the display device DSP, by controlling the orientation ofthe display device DSP such that a light source of the external light isnot visually recognized by the observer, the visibility of the displayedimage can be improved. Further, as a method of controlling theorientation of the display device DSP, the example of control of thesolar system SSYS explained with reference to FIGS. 14 and 15 can beapplied.

As described above, according to the present embodiment, a photodetectorand a display device which are small in size and low in cost can beprovided.

The present invention is not limited to the embodiments described abovebut the constituent elements of the invention can be modified in variousmanners without departing from the spirit and scope of the invention.Various aspects of the invention can also be extracted from anyappropriate combination of a plurality of constituent elements disclosedin the embodiments. Some constituent elements may be deleted in all ofthe constituent elements disclosed in the embodiments. The constituentelements described in different embodiments may be combined arbitrarily.

What is claimed is:
 1. A photodetector comprising: a sensor unitcomprising at least one photosensor; a liquid crystal element comprisinga first substrate comprising a plurality of first control electrodes, asecond substrate comprising a second control electrode, and a liquidcrystal layer held between the first substrate and the second substrate;a liquid crystal controller which controls a voltage to be applied tothe liquid crystal layer for forming a first lens that is opposed to thephotosensor in the liquid crystal layer; a sensor controller whichcontrols the sensor unit; and a memory unit which stores a first voltagefor forming the first lens of a first shape in the liquid crystal layer,and a second voltage for forming the first lens of a second shapedifferent from the first shape in the liquid crystal layer, wherein thesensor controller measures an output from the photosensor when the firstvoltage is applied to the liquid crystal layer, measures an output fromthe photosensor when the second voltage is applied to the liquid crystallayer, compares the outputs measured at the respective timings, anddetermines an incident direction of light according to a shape of thefirst lens at a timing when a maximum output is obtained.
 2. Thephotodetector of claim 1, wherein each of the first control electrodesis a strip electrode.
 3. The photodetector of claim 1, wherein the firstshape is symmetrical with respect to a normal of the liquid crystalelement, and the second shape is unsymmetrical with respect to thenormal of the liquid crystal element.
 4. The photodetector of claim 1,wherein a thickness of the liquid crystal layer is 10 to 100 μm.
 5. Thephotodetector of claim 1, wherein the first substrate further comprisesa first insulating substrate, a first insulating film, and a firstalignment film, the photosensor is arranged between the first insulatingsubstrate and the first insulating film, the first control electrodesare located on the first insulating film and are covered with the firstalignment film, the first control electrodes are located closer to theliquid crystal layer than the photosensor, and a space between two firstcontrol electrodes overlaps the photosensor.
 6. The photodetector ofclaim 5, wherein the second substrate further comprises a secondinsulating substrate and a second alignment film, and the second controlelectrode is arranged between the second insulating substrate and thesecond alignment film.
 7. The photodetector of claim 6, wherein thesecond substrate further comprises a light-shielding body, thelight-shielding body is arranged between the second insulating substrateand the second alignment film, and includes an opening, the opening isformed at a position opposed to the photosensor, and the second controlelectrode is arranged between the second insulating substrate and thesecond alignment film in the opening.